The flue dust in a known conveyor and cooler (VGB Kraftwerkstechnik 63 [1983], 422-27) is conveyed by compressed air to a system of air locks while simultaneously being cooled to the desired final temperature. Since the temperature of the dust is approximately 850.degree. C., the injectors that the conveying air is supplied through are subject to severe wear that leads to premature failure of those sections of the plant.
Eliminating a system of air locks consisting of two tanks and orienting the cooler pipes in such a way that the direction of flow of the mixture of dust and gas is repeatedly abruptly altered, generating pressure reductions as the result of sequential flection losses is also known (EP Pat. No. 0 108 505). The pipes in a flue-dust conveyor and cooler of this type must be precisely bent in order to prevent erosion. Furthermore, the dust can only be cooled to 150.degree. to 200.degree. C. because, if the temperature drops below the dew point, deposits will form on the inner surface of the pipes and impede conveyance of the dust. The resulting final temperature does not allow unobjectionable removal of the dust.